1: Heat oil over medium heat in medium sized skillet. Add vegetables, oregano, salt and pepper. Cook, covered, stirring occasionally for about 5-8 minutes, or until vegetables are soft. Let cool. Combine with ground beef and form into 4 patties.
2: Preheat barbeque grill to high. Lightly brush one side of each patty with oil. Place oiled side down on hot grill and then oil top side. Cook, about 5 minutes per side or until an internal temperature of 160°F (71°C) is reached.
3: To assemble, spread bottom of hamburger bun with about ½ tsp (2mL) Dijon mustard and 2 slices of pickles. Place patty on top, then top with ham, 2 more pickles and Swiss cheese. Spread ½ tsp (2mL) Dijon mustard on top bun, and place over toppings.
4: Wrap tightly in foil and return to barbeque. Place a very heavy object on top of burgers. Cook 3-5 minutes. Cheese will be bubbly and melted. Carefully remove brick and unwrap. Serve immediately.